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Updated: Sept 18, 2025
Leptonica is a pedagogically-oriented open source library containing software that is broadly useful for image processing and image analysis applications.
The official distribution, including all releases, is on GitHub: github.com/danbloomberg/leptonica.
Featured operations are
- Rasterop (a.k.a. bitblt)
- Affine transformations (scaling, translation, rotation, shear) on images of arbitrary pixel depth
- Binary and grayscale morphology, rank order, and convolution
- Seedfill and connected components
- Image transformations combining changes in scale and pixel depth
- Pixelwise masking, blending, enhancement, arithmetic ops, etc.
Ancillary operations include
- I/O for standard image formats
- Utilities to handle arrays of image-related data types
- Utilities for generic stacks, queues, heaps and lists; and for byte queues and arrays of numbers and strings
Example applications include
- Octcube-based color quantization, with and without dithering
- Modified median-cut color quantization, with and without dithering
- Skew determination of text images
- Segmentation of page images with mixed text and images
- jbig2 unsupervised classifier
- Border representations of 1 bit/pixel images and raster conversion for SVG
- PostScript generation (levels 1, 2, 3) of images for device-independent output
- PDF generation (levels 1, 2) of images for device-independent output
- Dewarping images of text taken with a camera
- Book-adaptive text recognition
- Rendering text on an image
- Connectivity-preserving thinning and thickening of 1 bit/pixel images
- Line removal from a grayscale sketch
- Search for least-cost paths on binary and grayscale images
Reference documentation for users
- The Leptonica image processing and analysis source code comes with a very weakly restricted copyright license.
- The README gives an overview of installation and usage, with a brief description of the library contents.
- A page of brief notes on version changes.
- A high-level view of the source files in the library.
- For a deeper look into specific components of the library, see the web pages linked from theimage processing page.
- Over 10 years ago, Tom Powers built the Unofficial Leptonica Documentation. This documentation contains anecdotes and information about algorithmic approaches in readable form. However, the README and other information about the software is based on version 1.68, and is far out of date. The ancient versions of leptonica referred to in those pages have not been supported for over a decade.
- Uncompleted sets of somewhat detailed usage notes and a lightweight overview have been attempted but are unlikely to be completed anytime in the current millenium.
- The final arbiter is, of course, the source itself.
Source download
- Click here to download the source. [ update: Sept 18, 2025 ]
- See here for further information about the source code.
Fun stuff
- What is the origin of the name Leptonica?
- Image processing at this site [ update: Sept 18, 2025 ]
- Some issues in software design
- A primer on particle physics
- A small collection of interesting links
- Broadband for Dummies: a primer for safely using the internet with windows
Contact: Dan Bloomberg (bloomberg "at" ieee "dot" org) for questions and suggestions
This documentation is licensed by Dan Bloomberg under a Creative Commons Attribution 3.0 United States License.